Wankel engine rotors may include straight radial ribs extending between the flanks and bearing support, such as to provide adequate stiffness while minimizing the rotor weight. However, particularly under high power which simultaneously imparts high thermal load on the rotor flanks and high structural loads on the bearing, the ribs may pull on the bearing support, which may cause it to deform and adversely impact the bearing load-carrying capacity. Moreover, the expansion of the flanks caused by the high temperature may produce an undesirable pinching of the apex seals.